Getting started with TeX, LaTeX, and friends

What's going on here?

TeX is a typesetting language. Instead of visually formatting your
text, you enter your manuscript text intertwined with TeX commands in a
plain text file. You then run TeX to produce formatted output, such as
a PDF file. Thus, in contrast to standard word processors, your
document is a separate file that does not pretend to be a representation
of the final typeset output, and so can be easily edited and manipulated.

Here are a couple of links with further background:

The levels of TeX web page explains
some of the most common components and terms used throughout TeX.

Since TeX predates the Internet, let alone the web, it has a long
tradition of documentation being available in book form. (Not to
mention being a typesetting program!) Here are the books we recommend
most highly.

The basic procedure is to create plain text files in any editor or
GUI front end (TeXworks, TeXShop, GNU Emacs, etc.), and
then run pdflatex myfile.tex from a command line to get
PDF output. Or run latex to get DVI output, instead of PDF.